Outcomes in Occult Spinal Dysraphism

  • Jeffrey P. BlountEmail author


Occult dysraphic lesions vary significantly. Some give rise to focal tether, and others can induce harm via more than one pathophysiological mechanism. Dermal sinus tracts threaten both by focal tether and as potential portals for infection. The tethering tract is distinct from the neural elements, so risks of neurological injury from surgical untethering are very low though the natural history is threatening. Similarly, split cord malformations (types I and II) are well-established sources of focal tether that demonstrate adverse natural histories when untreated. They can be complex and often accompany open forms of dysraphism but almost uniformly respond favorably to surgical untethering.

Lipomas are the most controversial of the dysraphic lesions. Filum lipomas are common and are often asymptomatic and of dubious pathological significance. There is virtually no controversy regarding surgical clipping of a fatty filum when the filum is thick and fat infiltrated, the conus is low, and there are symptoms consistent with tether. Surgical clipping of filum lipomas has few risks and low morbidity. However, the operative indications for filum clipping for cases that are asymptomatic or where the conus is in the normal position remain controversial. The evidence supporting these procedures is of modest power and quality.

Lipomas of the conus medullaris are the most difficult lesions to manage. Many but not all patients harboring these challenging lesions show progression of neurological decline over time. Many series attest to stabilization or improvement after operative intervention. However, tethering symptoms recur at a high rate (at least 50%) when follow-up is extended. Tether is one of several pathophysiological mechanisms in conus lipomas. There is general consensus that symptomatic patients should be offered surgery, but the role for prophylactic surgery is more variable, complex, and controversial. There are three conceptual approaches. The conservative approach involves reserving any operative intervention for clearly documented clinical or urodynamic decline. The optimum safe resection approach is widely embraced and strives to untether and reduce the volume of fat to the maximum safe extent to enable placode closure but not gross total removal of all fat. The radical approach embraces complete removal of the fatty mass, re-establishment of external pial surfaces, and optimization of the sac-cord ratio to prevent re-tether.


Outcomes Surgical outcomes Natural history Lipoma Dermal sinus tract Split cord malformation 


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Authors and Affiliations

  1. 1.Pediatric Neurosurgery, Children’s of AlabamaBirminghamUSA

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